Method of making drawing dies



Jan. 23, 1934. A. P. ROUX METHOD OF MAKING DRAWING DIES Filed Sept. 12, 1929 INVENTOR c ov'ow Pam ,M, omm M ATTORNEYS Patented Jan. 23, 1934 I 1,944,758 7 METHOD OF MAKING DRAWING DIES Adrian P. Roux, Oriskany, N. IL, assignor to General Cable Corporation, New York, N. Y., a corporation of New Jersey Application September 12, 1929 Sedal No. 391.994

14 Claims. (CL 26-107) This invention relates to a method of making drawing dies and has for an object the provision of an improved process whereby a superior die isproduced. v

Although there is a constantsearch for substitutes for diamond dies, up to the present time none has been found which possesses all the desirable qualities of diamond. But diamonds are very expensive, especially in larger sizes, and are dificult to mount satisfactorily. They are also brittle and have other undesired characteristics. As will be disclosed hereinbelowI have provided a mounting for diamonds or other hard die cores which permits the use of very small sizes, and which furnishes so substantial a backing or matrix for them that their tendency to split is greatly reduced and they can be used until only a thin shell or ring remains.

It has been the practice to some extent to cast a body or matrix of iron, steel, bronze or other metal upon the diamond or other hard object as a core and then to pierce the blank thus formed through the hard core to form the die. But the matrix materials heretofore used or proposed have not proven satisfactory. They are not sufficiently hard or are too ductile or too elastic to properly take the strains transmitted through the core; or they do not closely overlie and conform to the core due to improper shrinkage or nonso affinity for the core-piece. According to the present invention a suitable matrix material and a proper process of surrounding the core piece therewith have been discovered so that the resultant die is adequately backed, the matrix material being sufliciently hard, inelastic, non-ductile and non-brittle so that it will not readily split nor permit the core piece to split and so closely and evenly overlying the core piece that no inequality of strain is permitted. Indeed, in the case where a diamond core is used the matrix material is found to be so closely adherent to the core as apparently to form a union therewith.

The nature and objects of the invention will be better understood from an exposition of an exemplary and illustrative embodiment thereof when considered in connection with the accompanying drawing, wherein:

Figure 1 is a cross-section of a die and holder, the view being taken on the line -1-1 of Figure 2; s

Figure 2 is a plan view thereof; and

Figure 3 is a section through a mold assembly with the die in process of formation therein.

As shown in the drawing a hard core 10, for

example a diamond, is encased in a matrix 11 of the desired material. These elements forming the die proper are closely fitted into a holder 12 and if desired may be driven or welded therein. The assembly thus formed is in condition 60 for mounting in a drawing machine so as to have wire or the like drawn therethrough in the direction of the arrow A- in Figm'e 1.

The matrix material at present preferred may have the following composition:

Percent Ir 10 Nickel 15 Tungsten 30 Tungsten carbide 45 m But either iron or nickel may be used without the other in the composition, or the tungsten may be omitted, or the ratios of the various constituents may be varied. In some cases cobalt may be. substituted for the iron or nickel or tungsten or all of them. In any case the composition formed will be extremely hard and tough and will have good die-forming qualities of itself.

The die may be formed in a welding-carbon mold 15 disposed between water-cooled electrodes E1 and E2. The matrix material is preferably finely divided (say 300 mesh) tungsten carbide and metal which have been thoroughly mixed. The diamond or other core piece is held centered by projections 16 formed on the ends of carbon plugs 17 which also confine the matrix material about the core piece.

When thus assembled a considerable resilient pressure (say 1100 pounds per square inch) is imposed upon the carbon plugs 17 and electric current is turned on the electrodes. This sinters the matrix material and causes it to shrink in volume, the projections 16 of the carbon plugs 1'7 burning away or breaking down sufilciently to allow the plugs to follow-up and maintain pressure upon the matrix material.

The carbon mold, as shown in the drawing, entirely encloses the mold cavity and when the mold is heated it naturally maintains a reducing atmosphere which prevents oxidation of the core and the matrix material which is sintered thereabout. The rapid heating which is produced by the electric current'sinters the material rapidly so there is less opportunity for the core to be disintegrated. This produces a die in which the core is solid and sound. The matrix material being sintered instead of melted never becomes sufficiently fluid to permit the core readily to become displaced therein, the small carbon projections no being sufflcient, even if broken during heating to keep-the core in position.

After sintering the pressure is left on the-plugs while the die blank is allowed to cool between the water-cooled electrodes.

Upon cooling, the die blank thus produced is pierced through the core piece with the restricted portion of the pierced bore where the greatest drawing strains will be imposed located in the hard core piece. Normally the indentations in the blank left by the plug projections 16 serve to locate the line of piercing. The blank is then mounted in the holder 12 ready to be placed on a machine.

After the bore has become worn by use it may be re-bored for larger sizes and this may be repeated until the core is practically all used up to a thin outer shell. This benefit is attained in part because of the superior matrix material provided which is so hard and otherwise suitable that it may itself well serve for the flaring portions of the drawing bore.

Furthermore, with such a matrix, much smaller diamonds or other hard cores may be successfully used initially than with any known settings. For example, where 4 carat diamonds were formerly used for steel settings, and 1 carat diamonds for bronze settings, carat diamonds can by the present invention be used with equally good results; and likewise where 1 carat diamonds were required for steel settings and 4 carat diamonds for bronze settings, carat diamonds can now, be used. The saving, it will be realized, will be much greater than is represented by the proportions in size because of the fact that diamonds and other gems are disproportionally cheaper in the smaller sizes.

Also the cost of manufacture is greatly reduced by the present process. By comparison in a large shop it has been found that sixty (60) of the new die settings can be made in the time that was formerly required to make ten (10) by the old processes and materials. But above this is the fact that the dies made according to the present invention are practically all found by test to be free of faults while cast-metal set dies previously made were subject to'many flaws and faults, most of which could not be readily detected. So that, not only the settings, but the much more valuable cores were frequently broken before they had given much service in the expected way.

In service the setting material is unaffected by high temperatures which formerly rendered useless dies having settings of other materials such as steel, bronze, etc.

The above description of the particular embodiment of the invention is illustrative merely and is not intended as defining the limits of the invention.

What I claim is:

1. The method of manufacturing a drawing die which comprises holding a hard core piece between projections on carbon plugs in a carbon mold filled between the plugs about the core piece with a finely divided mixture of tungsten carbide and a metal, sintering the mixture by an electric current while pressure is maintained upon the material within the mold, the projections breaking down to permit continued pressure on the material as it shrinks about the core,

- cooling the die blank so formed while the pressure is maintained, and piercing the blank through the core at the depressions left by the plug-projections.

2. The method-of manufacturinga drawing die which comprises holding a hard natural gem core piece between carbon plugs in an enclosed carbon mold filled between the plugs about the core piece with a finely divided mixture of tungsten carbide and a metal, sintering the mixture by an electric current while maintaining pressure by carbon members upon the material within the mold, cooling the die blank so formed while the pressure is maintained, and drilling said core piece and said sintered material to form a die.

3. The method of manufacturing a drawing die which comprises embedding a hard natural gem core piece in a matrix including tungsten carbide sintered thereabout under pressure, and

drilling said core piece and said sintered material to form a die.

4. The method of manufacturing a drawing die which comprises embedding a diamond core piece in a matrix including tungsten carbide sintered thereabout under pressure and non-oxidizing conditions, and drilling the core piece and matrix to form a die.

5. The method of manufacturing a drawing die which comprises electrically sintering in situ a finely divided tungsten carbide material under pressure about a hard core piece which is of the same order of hardness and thereafter piercing the blank thus formed through the core piece and matrix, whereby the matrix material forms flared approaches to the core.

6. The method of manufacturing a drawing die which comprises, holding a hard core piece between carbon plugs in a carbon mold filled between the plugs about the core piece with finely divided tungsten carbide, sintering the mixture by an electric current while pressure is maintained upon the contents of the mold by carbon members, and drilling the core piece and the tungsten carbide covering to form a die.

7. The method of making a drawing die which comprises, placing the components of a hard metal carbide composition in unconsolidated finely divided condition in a mold about a core which is of the same order of hardness as the composition, heating the same to consolidate the carbide alloy and form a matrix of it about the core, and drilling the core piece and matrix to form a die.

8. The method of making a die which comprises, surrounding a diamond core with the fluent finely divided unconsolidated components of a composition closely related to the diamond in having a high melting point, great hardness, low ductility, these characteristics being above the range of high speed steels, consolidating the alloy under pressure at a high temperature and under non-oxidizing conditions to form a closely conforming matrix about the diamond core, and drilling the core and matrix to form a die.

9. The method of making a die which comprises, surrounding a core suitable in characteristics for drawing purposes with the fluent finely divided unconsolidated components of a composition closely related to the core in having great hardness, high melting point and low duetility, these characteristics being above the range of high speed steels, consolidating the alloy under pressure at a high temperature to form a closely conforming matrix about the core, and drilling the core and matrix to form a die.

10. The method of manufacturing a drawing die which comprises, placing a hard core in the hardness scale with diamonds, rubies and the like in a carbon mold, filling the mold on all sides of the core with a powdered matrix material adapted when sintered to form a matrix about the core of the same hardness range as the core itself, completely enclosing these die components with the carbon mold, sintering the matrix material about the core, maintaining pressure upon the matrix material while it is being sintered, and drilling the core and matrix to form a die.

11. The method as set vforth in claim 10 in which the core piece is held at the center where it will be pierced, by small supporting members which can be disintegrated during heating.

12. The method as set forth in claim 10 in which the core is a diamond and in which the matrix is principally a hard metal carbide.

13. The method of manufacturing a wire drawing die which comprises, enveloping a diamond core within a mass of finely divided particles including a material which closely approaches the diamond in hardness, applying pressure and heat to the particles to form a solid supporting structure for said core, and drilling said structure and core to produce a wire drawing die.

14. The method of manufacturing a wire drawing die which comprises, enveloping a diamond core within a mass of finely divided particles including tungsten carbide particles, applying pressure and heat to the particles to form a solid supporting structure for said core, and drilling said structure and core to produce a wire drawing die.

ADRIAN P. ROUX. 

